Process of making white lead



Oct. 22, 1929. E. c. WALKER PROCESS OF MAKING WHITE LEAD 2 Sheets-$heet 1 Filed Aug. 1921 Oct. 22, 1929. WALKER 7 1,732,490

PROCESS OF MAKING WHITE LEAD Filed Aug. 1921 2 Sheets-Sheet 2 3M i [arm/w C. MAKE/E;

Patented Oct. 22, 1929 EDWD C. WALKER, OF ST. LOUIS, MISSOURI, ASSIGNOR T0 NATIONAL LEAD 630M- PANY, OF ST. LOUI$, MISSOURT, A CORPORATION OF NEW JERSEY PRCCESS OF MAKING WHITE T1 Application filed August 11., 192i. hcrial No..489,002.

This invention relates to the manufacture of white lead and more particularly to the corrosion of the lead.

The corrosion of lead is accomplished in accordance with a number of methods, the Ignost important of which are the Dutch process and the Crerman or Chamber process.

In the Dutch process as practiced in the United States,lead buckles in the form of grids are placed in earthenware pots, each of which contains acetic acid; the loaded pots are then placed in layers separated by boards, and the whole is covered by moist spent tan bark and allowed to stand for about ninety days. The fermentation of the tan bark causes an evolution of carbon dioxide, heat and moisture, the resultant action of which is the corrosion of the buckles, that is, the formation of basic lead carbonate.

Tn the German or Chamber process the lead in the form of gratings is placed in a closed chamber of wood or brick work and subjected to the action of carbon dioxide, moisture and acetic acid. The carbon dioxide is obtained from the products of combustion from a coke furnace, which products of combustion also heat a boiler in order to furnish the supply of moisture in the form of steam, and heats an acetic acid pan to furnish the required acid vapor. The result is corrosion of lead in the formation of the basic lead carbonate. s

Th accordance with both processes, the lead and the corroded product must be handled, with the result that there .is liability of lead poisoning. This liability is so serious that under the laws of some countries, the manufacture of white lead is absolutely prohibited and in others; subject to strict regulations.

Both processes also cause the evolution of acid fumes which are uncomfortable as well as injurious to the workmen.

The Dutch process requires a large space and a long time; the result is that a large amount of money is tied up in metal and equipment, which together with the deterioration of the pots, lumber and tan bark, makes this process rather expensive. Furthermore spent tan bark is difficult to obtain at the present time on account of the use by tanners of extracts, so that this article is not as readily obtained at the present time as was formerly the case when tan bark itself was used altogether for the tanning of leather and where itwas obtainable close at hand so that the freight charges were not a serious item,

Tn the Chamber process the loading and clearing of the chamber is not only inconvenient but also exceedingly uncomfortable to the workmen and injurious to their health, so that it is ditficult and sometimes impossible to obtain and retain the required help. Fun thermore the equipment is expensive to con struct and maintain, and as in the Dutch process, a large amount of money is tied up fore, is to provide a process of corroding the lead, which will retain all of the advantageous features of the riorlprocesses and which will obviate he disadvantageous features.

Another object is to provide a process which is continuous in its operation, so as to in efi'ect furnish a steady flow of the corroded product.

Another object is to provide a process in which the lead is subjected to a slow corroding action which is so desirable, and in which the workmen will be protected against the poisonous efl'ects.

Another object is to provide a process which is subject to regulation and control and the operation of which is simple and economical.

Further objects will appear from the detail description taken in connection with the accompanying drawings, in which:

Figure 1 is a side elevation in somewhat diagrammatical form of an apparatus em-- they pass while subjected to the action of the corroding agents or gases. The stack is of suflicient extent so as to cause the gradual movement of the lead therealong, in order to secure the desired slow corroding action overan extended space of time. The action is, however, substantially continuous, the

metal being loaded or replenished at the top, while the corroded product is gradually withdrawn at the bottom.

It will, be noted that as the metal proceeds or rather flows along the stack, it will become graduall corroded, during which corrosion its speci cgravity will decrease. We, therefore, have the condition in which the specific gravity progressively increases from the bottom to the top of the stack, so that the different strata are successively subjected to an increasing burden, which not only increases with the height of the stack but also with the specific gravity. Since the buckles become weaker and more brittle as the corrosion proceeds, the different strata become successively weaker proceedingfrom the top to the bottom of the stack. The natural result, therefore, is that if the material in the stack is sub'ected to the overburden, the buckles are lia le to become crushed, thereby clogging thestack, interfering with the corroding action and causing the buckles to hang.

In accordance with this invention the overburden is relieved, that is, the successive strata are partly freed from the burden thereabove. This is accomplished by furnishing or providing the stack with an angle of relief, so that the weight of the load is partially transmitted to the stack 50 as to relieve the overburden.

In accordance with this invention, therefore, the stack is set at an angle with its bed at the angle of relief of the material. The buckles are made of a form adapted to roll along the bed and they are, therefore, made in the form of balls of more or less spherical form. These buckles are, however, made hollow and perforated in order to permit the gases to not only circulate over but in and through the same. By setting the bed of the stack at an incline at the angle of relief, or slightly greater than the angle of rest of the rolling material, the buckles are permitted to roll along the bed, and this incline can be so proportioned that the buckles can proceed gradually from the top to the bottom of the stack.

The corroding agents may be introduced into the stack in any suitable manner at any suitable point, such as near the bottom, and these corroding agents may be furnished in any suitable manner as by the usual coke furnace, steam boiler and acetic acid pan, the latter being heated by the products of combustion before they pass into the stack. In this way the required carbon dioxide, steam and acetic acid vapor may be conducted to the stack for action therein on the buckles passing therealong, and these gases and vapors may be closely regulated.

In the accompanying drawings, apparatus is shown for performing the process; it is understood, however, that the apparatu is only shown to illustrate the operation of the process and that it may be varied without departing from the spirit of this invention.

Referring to the accompanying drawings,

and more particularly to Figures 1 and 2, 1 designates a suitable frame work on which is supported a series of stack sections 2 and 3. These stack sections may be of wood, concrete or any other suitable material and the sections may be multiplied to provide a path of the extent required to complete the corroding operation. The top section may be provided with a hopper 4 to permit loading of the buckles therein and this hopper may be provided with a cover 5. The end section is provided with any suitable closure 6, which is constructed to permit the bottom or outlet to be opened for the withdrawal of the corroded buckles. At the intersection of two sections, a removable cover 7 may be provided to permit access, and the bed of the stack section thereabove may be extended as shown at 8 and 9 to provide for a return for the moisture. Observation openings 10 may be provided along the stack sections near their upper faces and these openings may be provided with removable covers 11. The sections may have arranged therealong cross members 12 which are perforated as shown at 13 to permit circulation of the gases and vapors.

The gases and vapors may be supplied to the stack in any suitable manner and by any suitable apparatus. Thus as shown in Figure 1, a coke furnace 14 is provided to generate the carbon dioxide, while the moisture is generated in the form of steam by a boiler 15 and the acetic acid vapor is generated by a pan 16; the products of combustion formed in the coke furnace 14 may pass around and under the boiler and the pan to heat the same, being then finally discharged by a pipe 17 provided with a damper or valve 18. The steam is delivered by a pipe 19 controlled by a valve 20 and a steam connection 21 controlled by a valve 22 is made to the pan 16; a valve 23 area-49o l7, l9 and 24 are connected to discharge the gases and vapors into the lower end of the .stack which may be accomplished through a suitable dome 26.

Referring to Figure 3, the buckle 27 is of spherical shape to provide a hollow ball structure. It is perforated to form a foraminous structure and this may be accomplished by slots 28 formed in the walls. In the actual onstruction of this buckle, it may be formed of a sheet of metal, laid out to a suitable pattern and slotted and this buckle may then be formed to shape in any suitable manner; It, therefore, forms a structure which is hollow and perforated, which presents a large surface and permits the gases to circulate therethrough and thereover. This buckle is, therefore, constructed to roll and in actual practice can be of a size suitable to meet the requirements. Thus it may be made of a diameter of about two inches or even less.

Tn Figure 1, where the stack sections are arranged in zig-zag relation, the buckles in passing from section to-section, turn completely over. This feature, therefore, insures that the buckles will be fully exposed on all sides.

Figures 4 and 5 show another embodiment of this invention in which the stack structure comprises instead of a .series of sections arranged in zig-zag relation, a helical structure providing a helical path. This stack structure'is shown at 102 as supported on frame work 101. In details of construction, the stack is in every way similar to the stack shown in Figures 1 and 2 and accordingly :1

detail description thereof is unnecessary. In order, however, to identify the parts, those parts in Figures 4 and 5 which correspond to the similar parts in El ures l and 2 are indicated by the same re erence characters with a cipher added.

The stack provides a structure which has an extended path; it will, of course, be understood that the number of sections and the length of each ismade 'to suit the requirements in order to provide a path length of sutticient extent to permit the buckles tobe corroded as they pass from the inlet to the outlet'of the stack.

The beds of the sections are arranged at,

such an'incline that the angle of incline will be greater than the normal angle of rest or relief of the buckle, so that these buckles can roll and move along the bed under. the action of gravity. The weight of overburden to which each stratum would be normally subjected if the stack were vertical is, therefore, transmitted mostly to the bed and stack structure so that the overburden is in fact relieved.

In the actual operation of the process, the

stack is filled with the metal buckles from the bottom to the top and the s and vapors are then delivered to the stack to act upon the buckles. Atshort periods the buckles are withdrawn from the bottom of the stack by opening the closure 6 and coincident with the withdrawal of these buckles, the metal is replenished at the top. This operation is repeated at intervals and day by day until a condition is finally obtained where the buckles arriving at the bottom are suficiently corroded; this stack is then in a condition where we have properly corroded buckles at the outlet and fresh metal at the top; the apparatus is now. in condition for continuous operation. Thereafter at short intervals, the corroded buckles are withdrawn from the bottom and coincidently metal is replenished at the top of the stack, the with-\ drawal of the buckles from the bottom causing these buckles to pass downwardly along the stack under the action of gravity. This procedure can then be followed day by day as a continuous operation. During the process the condition and procedure can be observed through the medium of the observa-. tion openings 10 and more completely by the door closed by the cover 7 and through these openings any hanging or sticking of the buckles can be obviated by poking or other loosening means.

The period consumed for a given buckle to pass from the inlet to the outlet'can be varied to suit requirements. As a matter of fact this process can conveniently be controlled so that the actual corroding action will be very similar to that, in the Dutch process, as the time required can be made to correspond to the time taken in the Dutch process, as the'stack structure can be made of sufficient dimensions to furnish the required bed extent in order to consume such time. Tn accordance With this invention, however, the process is not intermittent but continuous, as the metal is replenished at one end of the apparatus, while the corroded buckles are being withdrawn at the other end. The nature of the process and the ap paratus for practicin the same is, however, such that not onl is this continuous operation possible an practiced, but machinery can be provided for handling the metal as well as the buckles, such as conveyors 29 and 30 for respectively delivering the metal and taking away thecorroded buckles. Accordingly danger of poisoning is practically elimihated during the corroding process.

In addition to the mechanical conveniences brought about by the employment of this process and apparatus embodying this invention, it is found that the chemical action is more perfect and under better control. As the buckles pass along the stack, they roll over and over and, therefore, are subjected to fresh portions of th'd gases; moreover it is really insured that each buck 1e and each portion thereof will be subjected to the complete action of the gases. Moreover since the gases travel in a direction opposite to the movement of the buckles, the fresh gases will act on the more corroded buckles, while the weaker gases will act on the fresh metal and the less corroded buck les; accordingly maximum corrosion is insured within a minimum period and with minimum quantities of gases. Moreover during the entire process the corroding action can always be observed while this action is further under control by the provision of the valves delivering the corroding agents to the stack.

The angle of the stack bed need not be uniform along the entire bed considering the entire bed as including the bed sections of the different stack sections in Figure 1, and including the bed helices in Figure 4; but this angle may be made steeper as weproceed from the inlet to the outlet. This may be in fact desirable as the angle of relief or rest of the buckle does in fact increase as the buckle becomes corroded. This increasing of the bed angle may be readily accomplished by making the bed bottom of Figures 1 and 4 a gradually di'opping curve as we proceed from the inlet to the outlet. or in case of the sectional stack (Figure 1) by making each suceeding stack section steeper as we proceed from the inlet tothe outlet. The bed angle may. however, be made that of the angle of relief or rest of the completely corroded buckle, or

slightly greater, as this will insure rolling and flow of the buckles along the bed from the inlet to the outlet.

This invention, therefore, provides a process having all of the advantageous features of'the Dutch process and while obviating its disadvantageous features. The corroded product will, therefore, be at least the full equivalent of the corresponding product produced by the Dutch process, and the resultant pigment will have the desired high covering power, such as has been the characteristics of white lead made in accordance with the Dutch process.

It is obvious that various changes may be made in details without departing from the spirit of this invention; it is, therefore, to be understood that this invention is not to be limited to the specific details shown and described.

Having thus described the invention, what is claimed is 1. In the art of making white lead, the process comprising, corroding the interengaging lead buckles while in a stack in which the overburden is relieved.

2. In the art of making white lead, the process comprising, corroding the interengaging lead buckles while in a stack in which the 3. In the art of making white lead, the process comprising, corroding the interengaging lead buckles while in a stack having an angle of relief in order to relieve the over burden.

4. In the art of making white lead, the process comprising, corroding the lead while in a'stack, and gradually withdrawing the corroded lead from the bottom.

5. In the art of making white lead, the process comprising, corroding the lead While in a stack, and gradually withdrawing the corroded lead from the bottom while the metal is replenished at the top.

6. In the art of making white lead, the process comprising, corroding the lead while in a stack, and allowing the lead to gradually move along the stack while the corroded lead is withdrawn from the bottom.

7. In the art of making white lead, the process comprising. corroding the interengaging lead buckles while in an inclined stack, and allowing the lead to move along the stack.

8. In the art of making white lead, the process comprising, corroding the lead while in an inclined stack, and allowing the lead to move along the stack while the corroded lead is withdrawn from the bottom.

9. In the art of making white lead, the process comprising, corroding the buckles while supported to relieve the overburden.

10. In the art of making white lead the process comprising, supporting the buckles so as to permit them to roll, and subjecting them to corroding agents.

11. In the art of making white lead. the process comprising, supporting the buckles along an angle of relief so as to permit them to roll, and subjecting them to corroding agents.

12. In the art of making white lead, the process comprising, corroding the lead buckles while in a stack, and turning the buckles over while they pass along the stack.

13. In the art of making white lead. the process comprising corroding the lead buckles while they are passed along an inclined stack, and turning the buckles over during their passage.

14. In the art of making white lead, the process comprising, passing the lead along a stack, and passing the corroding agents through the stack in a direction opposite to the movement of the lead.

15. In the art of making white lead, the process comprising, allowing the lead to gradually move along the stack, and subjecting the same to corroding agents moving in a direction opposite to the flow of the lead.

In testimony whereof I atfix my signature this 14th day of July, 1921.

EDWARD C. WALKER.

weight of the lead is partially transmitted to the stack in order to relieve the overburden. 

